Lamp base



FIG. 1 is a perspective view taken from the left side of the new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a side elevational thereof;

FIG. 4 is a front elevation view thereof; and,

FIG. 5 is a bottom view thereof. 

We claim the ornamental design for a lamp base, as shown and described. 